Honestly, the first thing you should do is figure out what you want to do about the battery, IMO. Building one yourself from cells requires quite a few things like a spot welder, fishpaper, nickel strips, fishpaper rings, and probably some other stuff I’m forgetting. There are cheap options for spotwelders, and I’ve gotten away with that route, but a good one is pretty expensive, especially if you don’t have a car battery sitting around and don’t want to pull one from your car for the project.
Buying a battery built by someone else is quite expensive unless you find someone selling something used here.
Lipos are also an option if you want to do something DIY without building a battery from cells, but I don’t think they’re the best for range. I haven’t messed with them at all, though.
It sounds like you want to do a custom battery box, and if that is the case, those are probably your options.
As far as how the electronics are laid out: Beautiful diagrams! NO WORDS (SERIOUS) - #6 by Excess
has a bunch of stuff, but
is a good example IMO. That assumes you’re using a loop key, but there are options for ESCs with on/off features or anti-spark switches that don’t use loop keys.
Edit: Actually, I just realized that diagram would require the loop key for charging, which I don’t like, so I’d move it after the split in the charge port. It’s still an alright example, though.